The field of this invention involves the bending of conduit and specifically involves a device to give an indication whether the bend remains in the bending plane.
In the installation of electrical systems in commerical installations and in large buildings, it is necessary to encase the electrical wires in conduit or pipe as they are run from place to place within the building. Throughout this specification the term "conduit" is used to include not only the standard conduit, but also pipe and tubing which may be used to protect the electric lines. As the conduit is installed in the building, it is necessary to bend the conduit to avoid obstructions. A common shape is a "jog" wherein the conduit is bent in one direction and is then bent backward so that the remaining length of the conduit is pointed in the same general direction as it started, but at a different level. For the "jog" bend it is necessary to have the straight conduit before the bends and the straight conduit after the bends be in the same flat plane. Thus, both bends must be in the same bending plane or else the ends will not be extending in the same direction. Visual as well as practical considerations require that when looking down the length of conduit with multiple bends, that the bends be in a single plane. In particular, the bends must be coplanar.
Large conventional bending machines are available to form bends with planar precision but are not practical for use at the site of construction. Small plane indicators have been described but their operation is unweildly. These devices are described in the following United States Patents: U.S. Pat. Nos. 3,465,560 to Gardner, 3,396,565 to Miller, 2,932,225 to Gardner, 1,229,916 to Duncan, 2,624,118 to Anderson, 2,824,381 to Traupmann, 3,822,481 to Doan, 2,842,863 to Hellwig, 4,274,208 to Yakkel and 4,394,799 to Moree et al.
None of these devices satisfy the above needs or attain the objects described hereinbelow.